In-app purchase buttons have been disappearing from Apple iOS in recent days as some high-profile players---Amazon, Barnes & Noble and the Wall Street Journal---end direct sales from their respective apps. But the in-app purchase jousting is just beginning.

In-app purchase buttons have been disappearing from Apple iOS in recent days as some high-profile players---Amazon, Barnes & Noble and the Wall Street Journal---end direct sales from their respective apps. But the in-app purchase jousting is just beginning.

Recall that Apple changed its rules in February for content publishers on in-app purchases. If you linked to a store outside of the applications you had to include in-app purchases too so Apple could get a cut. Apple blinked a bit for newspapers and magazines. Jason Perlow predicted an judgment day for e-book apps, but was a few weeks too early.

On the surface, the reaction is simple. What choice did these companies have? If you want to be on iOS you have to play by Apple's rules. And iOS is a big chunk of market share. It's not like you can walk away. Amazon said:

This update removes the Kindle Store button from the app. Customers can shop for 950,000 books in the Kindle Store by visiting Amazon.com/kindlestore in Safari or any web browser.

So is this over? Not quite. I suspect that more companies are going the way of the Financial Times and develop HTML5 apps and skip Apple's App Store entirely. These first moves by rival e-book players are likely to be trial balloons. You remove a Kindle Store button evaluate sales and let the metrics decide. Rest assured that if these e-book store giants didn't have an installed base they would have already ditched Apple's App Store.

In a few weeks, those metrics may tell Kobo, Amazon and Barnes & Noble that an app isn't worth the effort. Perhaps they all go HTML5 at some point. The writing on the e-book wall appears to be that content needs to come from iBooks.

Another wrinkle to ponder is that Amazon also has a tablet on deck. This tablet will feature Kindle apps---potentially natively on Android---and that move will make the Apple relationship contentious. In advance, Amazon is likely to push HTML5 sooner than later.

In other words, the strategy appears to be that it makes sense to cave to Apple now, monitor and then move to HTML5. These players will say screw iOS here's the HTML5 version. What remains to be seen is how joint customers will react. Today a few buttons disappear, but the back-and-forth is likely to continue. The end destination is likely to be HTML5. There could actually be an iOS exodus that's just starting. Will players like Netflix and Spotify---also caught in the in-app purchase skirmish---stick with crippled iOS apps?